This invention relates to stents which are implanted in the body.
Stents are used in body lumens, such as blood vessels to maintain them in an open condition. Typically, the stent is delivered into the lumen by a catheter that supports the stent in a compact form during percutaneous insertion and transport through a lumen, such as a vessel, to the desired implantation site. Upon reaching the site the stent is expanded so that it engages the interior wall of the vessel. The catheter is then removed, leaving the stent in the body.
The expansion of the stent may involve forcing it to expand radially outwardly as by inflation of a balloon carried by the catheter or the stent may be of a self-expanding type, several of which are known in the art. For example, the stent may be made of a memory metal such as NITINOL which self-expands in selected temperature ranges.
It can be readily seen that the more flexible the stent is during percutaneous insertion the more easily it can negotiate bends and curves in the lumen or vessel to reach the implantation site.
This invention provides a stent design of individual annular elements shaped so as to loosely interfit or interlock together with or without intersection and without cross-over points whereby the stent exhibits unusual flexibility.
Preferably, the annular elements are multiple independent serpentine-like rings adjacent to each other having laterally spaced segments 180xc2x0 out of phase with each other to provide a stepped sequence around each ring, each segment having a wide and a narrow intermediate portion with one set of segments on one side being fitted into an adjacent set of segments on one side of an adjacent serpentine ring to interlock the rings together against longitudinal separation thus forming a flexible cylindrical or tubular structure.
In another aspect of the invention, the edges of the annular rings may be formed at an angle with respect to the center line of the tubular stent configuration rather than aligned therewith as in the prior art. By fabricating the stent with such angular side walls xe2x80x9coff centerxe2x80x9d the rings will interlock with one another against radial separation if moved radially in or out with respect to the stent centerline.